Tertiary alcohol stabilized E-series prostaglandins

ABSTRACT

A stabilized pharmaceutical composition comprising an E-series prostaglandin and a saturated aliphatic tertiary alcohol having from 4 to 10 carbon atoms.

United States Patent Monkhouse Dec. 16, 1975 TERTIARY ALCOHOL STABILIZED E-SERIES PROSTAGLANDINS [56] References Cited [75] Inventor: Donald C. Monkhouse, Waterford, UNITED STATES PATENTS v 3,749,800 7/1973 Stehle et al. 424/318 73 Assigneet Pfizer Inc New York, N'Y' 3,833,725 9/1974 Thompson 424/243 [22] Filed: 1974 Primary ExaminerSam Rosen [21] A l N 462,213 Attorney, Agent, or Firm-Connolly and Hutz 52 US. Cl. 424/45; 260/468 D; 260/514 D; [571 ABSTRACT /557 R; /30 2 /320 A stabilized pharmaceutical composition comprising [51] Int. Cl. A61K 9/12; A61K 31/19; an E-series prostaglandin and a saturated aliphatic ter- CO7C 19/74; C07C 103/37 tiary alcohol having from 4 to 10 carbon atoms.

[58] Field of Search 424/305, 318, 45, 317;

260/468 D, 514 D, 557 R 8 Claims, N0 Drawings TERTIARY ALCOHOL STABILIZED E-SERIES 'PROSTAGLANDINS BACKGROUND OF THE INVENTION This invention relates to stabilized pharmaceutical compositions of prostaglandins. In particular, itrelates to saturated aliphatic tertiary alcohol containing compositions of biologically active E-series prostaglandins or their analogs. The prostaglandins of the E-series are those which have at the nine position a carbonyl and at the eleven position a hydroxy.

The prostaglandins are C-20 unsaturated fatty acids which exhibit diverse physiological effects. For instance, the prostaglandins of the E-series are potent vasodilators (Bergstrom, et. a1., Acta Plrvsiol. Scand. 641332-33, 1965 and Bergstrom, et 211., Life Sci. 6:449-455, 1967) and lower systemic arterial blood pressure (vasodepression) or intravenous administration (Weeks and King, FederationProc. 23:327, 1964. Bergstrom, et al., 1965, op. cit; Carlson, et al., Acta Med. Scand. 183:423-430, 1968; and Carlson, et al., Acta Plrvsiol. Scand. 75: 16 1-169, 1969). Another well known physiological action for PGE and PGE is as a bronchodilator (Cuthbert, Brit. Med. J. 4:723-726, 1969). Another physiological action'for PGE is to increase nasal patency Jackson, Curr. Ther. Res. 12:711-17, 1970).

Still another important physiological role for the natural prostaglandins is in connection with the reproductive cycle. PGE; is known to possess the ability to induce labor (Karim, et al., J. Obstet Gynaec. Brit. Cwlt/z. 77:200-210, 1970), to induce therapeutic abortion (Bygdeman, et al., Contraception, 4, 293 (1971) and to be useful for control of fertility (Karim, Contraception, 3, 173 1971)). Patents have been obtained for several prostaglandins of the E-series as inducers of labor in mammals (Belgian Pat. No. 754,158 and West German Pat. No. 2,034,641). In addition, a known physiological activity of PGF is synchronization of oestrus in domestic animals (Inskeep, J. Animal Sci., 36, 1149, 1973).

Still other known physiological activities for PGE are in the inhibition of gastric acid secretion (Shaw and Ramwell, In: Worcester Symp. on Prostaglandins, New York, Wiley, 1968, p. 55-64) and also of platelet aggregation (Emmons, et al., Brit. Med. J. 2:468-472, 1967).

The application of prostaglandins in a number of areas has been severely hampered by their apparent instability, especially in solution. Karim, et al. (Eur. J. Plzarmacol. 4, 416, 1968) measured the biological activity of saline solutions containing 100 ng/ml PGE PGE and PGF stored at various pH values at room temperature. The PGE compounds showed 25-40% loss of biological activity after 60 days at pH -7, while the PGF compounds were still fully active after 182 days. Other prostaglandin stability studies have been carried out by Andersen (J. Lipid. Res., 10, 320, 1969), Brummer (J. Pharm. PharmacoL, 23, 804, 1971) and others and show similar results. The need for a method of storing solutions of E-series prostaglandins for long periods of time will be readily apparent.

SUMMARY OF THE INVENTION The present invention satisfies this need by providing a stabilized pharmaceutical composition for comprising a biologically active prostaglandin of the E-series and a saturated'alip'hatic tertiary alcohol having from 4 to 10 carbon'atomssaid prostaglandinbeing present in the arnounrof'froj'm aboutOLOOS to 0.500% by weight of compositionl The composition is preferred in which the prostaglandin is PGE, orPGE and especially when the PGE is N-acetyl'or- N-benzoyl PGE carboxamide of the formula:

wherein: R is methyl or phenyl.

Also preferred is the composition wherein the prostaglandin is present in the amount of from about 0.010 to 0.100% by weight.

Another preferred form of the novel composition of the present invention is that in which a halogenated hydrocarbon propellant of up to 2 carbon atoms is also present, said propellant being employed in the amount of 1 to 10 parts by volume, per part of said alcohol.

DETAILED DESCRIPTION OF THE INVENTION The synthesis of the natural prostaglandins of the E-series has been performed by Prof. E. J. Corey and his co-workers (Corey, et al., J. Amer. Chem. 500.. 92, 2586 1970); and references cited therein), and E-series prostaglandins made by the reaction sequence as well as those made by other schemes or isolated from natural material are suitable for use in the compositions of this invention. Also suitable in the processes of this invention are 15-lower alkyl derivatives of the natural prostaglandins such as are described by G. Bundy. et al., Anal. NY. Acad. SCL, 180, p. 76, 1971.

The N-substituted prostaglandin carboxamides such as N-acetyl and N-benzoyl-PGE carboxamide, described in U.S. Ser. No. 260,518 filed June 7, 1972; the tetrazoyl derivatives of prostaglandins disclosed in U.S. Ser. No. 177,102 filed Sept. 1, 1971; the oxaprostaglandins disclosed in U.S. Ser. No. 259.215 filed June 2, 1972; the p-biphenyl esters of w-nor substituted prostaglandins such as 16-phenyl-l3,14-dihydro-mtetranor PGE p-biphenyl ester, described in U.S. Ser. No. 304,815 filed Nov. 8, 1972; and the (ii-substituted pentanorprostaglandins such as l6-p-biphenyl-mtetranor PGE and l6-(a-thienyl)-urtetranor PGE disclosed in U.S. Ser. No. 271,220 filed July 13, 1972 are especially important examples of biologically active prostaglandins of the E-series useful in the compositions of the present invention. The disclosures of the above named U.S. patent applications are incorporated herein by reference.

For the first step in the preparation of the N-substituted prostaglandin carboxamides, the appropriate hemiacetal precursor is caused toreact with the disodium salt of a novel N'-substituted carboxamide butyltriphenylphosphonium bromide, in a molar ratio of from about 1:2 to 1:5. Such precursors are as follows:

2- 5a-hydroxy-3 a-( tetrahydropyran-Z-yloxy )-2/3 3a-( tetrahydropyran-Z-yloxy )-trans- 1 -octen- 1 yl)cyclopent-1a-yl]acetaldehyde, y-hemiacetal for PGE PGE and 13,14-dihydro-PGE Compound xxvn is reduced with H /Pa to give the saturated hemiacetal XXVIII.

Alternatively, Compound XXIII can be reduced with zinc borohydride to produce compound XXIV wherein R is hydrogen. This latter compound may be carried through an analogous series of steps to produce hemiacetals I and VI.

The reaction will preferably be carried out at temperatures of about 2565C. in an inert solvent such as dimethylsulfoxide and in an inert atmosphere, for a period of up to about 4 hours or until the reaction is essentially complete.

The substituted.carboxamide-containing intermediates produced in the firststep, as described above, may be converted by. published procedures Corey. et al., J. Am. Chem. 500,, 93, 1490 (1971) to the N-substituted carboxamide analogs of any of the prostaglandins listed above. These procedures are further described in detail in preparations A A below and the steps entailed are summarized in the reaction schemes A and B below. wherein R is alkanoyl, cycloalkanoyl, or alkenoyl of from 2 to l0 carbon atomsiaryoyl or substituted aryoyl from 7 to 11 carbon atoms wherein said substituents may be methyl, halogen, or methoxy; alkylsulfonyl from 1.,to 7 carbon atoms; phenylsulfonyl or mono-substitutedphenylsulfonyl wherein said substituent may be methyl, halogen, or methoxy; styrylsulfonyl; or Z-thiophenesulfonyl; and TH? is tetrahydropyranyl.

The utility of these prostaglandins is the same as for the naturally occurring E-series prostaglandins. For example, a stabilized solution of N-acetyl or N-benzoyl lGE -carboxamide is employed as nose drops to increase nasal patency using a dosage of from about 10-500 #g/dose. For bronchodilator use, a stabilized solution of N-acetyl or N-benzoyl PGE carboxamide is employed either as an oral spray or a pressurized Freon-containing aerosol using a dosage of from 10-500 pug/dose.

REACTION SCHEME A PGE N-substituted carboxamide -continu'ed 13 l l-dihydro-PGE N-substituted carboxamidc REACTION SCHEME B VII As shown in Reaction Scheme A, Hermiacetal I is caused to react with the novel reagent II to produce III, the N-substituted carboxamide analog of the bis-TI-IP ether of PGF III PGE -N-substituted carboxamide requires treatment with Jones reagent to form a second intermediate before the acid treatment and purification as above.

III PGE -N-substituted carboxamide follows exactly the same method as outlined for the PGE above.

Ill l3,l4-dihydro PGE N-substituted carboxamide requires a reduction with palladium on carbon and methanol to produce V which is then hydrolysed with aqueous acetic acid, and purified as above.

To produce the other 13,14-dihydro derivatives one follows the procedures outlined above. Alternatively the PGE -N-substituted carboxamides may be reduced with palladium on carbon in methanol to produce the l 3, l4-dihydro PGE -N-substituted carboxamide.

13, 14-- dihydro-PGE N-substituted carboxamide Referring now to Reaction Scheme B, Hemiacetal VI is caused to react with the novel reagent II to produce VII, the N-substituted carboxamide analog of the bis- Tl-IP ether of 13,14-dihydro PGF VII l3.l4-dihydro PGE -N-substituted carboxamide requires treatment with Jones reagent to form a second intermediate before acid treatment and purification as above.

To produce the l5-lower alkyl derivatives of all of the above mentioned prostaglandin N-substituted carboxamides. one merely employs a hemiacetal I or hemiacetal;VI with a lower alkyl moiety in the 15 position and proceeds as above to produce the desired compound.

To produce PGE N- substituted carboxamide, hemiacetal VIII is employed as the starting material and all of the other reaction steps are identical to those given above.

Alternatively, the- N-substituted prostaglandin carboxamides may be prepared by treating the appropriate prostaglandinacid precursors with an acyl' isocyanate followed by hydrolysis of the tetrahydropyranyl groups as outlined in Reaction Scheme C. The appropriate precursors X-XIV are known compounds (Corey, et al., J. Am. Chem. 500., 92. 397 (1970); ibid.. 92. 2586 (1970); ibid., 93, 1490 (1971)).

For the first step in the preparation of the tetrazoyl derivatives of prostaglandins, the appropriate hemiace- VIII tal precursor (I. VI, VIII) is caused to react with the REACT ION SCHEME C O k I PGE R N=C=O N-substituted carboxamide PG E v RCN=G=O H N-substituted carboxamide IX 13, l I-dihydro PC1112 I IX carboxamide XII ' PGE3 RCN=C= li-substituted carboxamide o I R N=C=O 3, ih'ydro PGE III-substituted IX carboxamide XIV disodium salt of a novel tetrazoylbutyltriphenylphosphonium bromide (XV). in a molar ratio'of from about e I 1:2 to 1:5. Such precursors may be converted to the Q N' tetrazoyl analogs of any of the -prostaglandins listed as 5 C'HBMPCHZCHBC ll. described above for the N-substituted' c2irbox2amide analogs.

REACTION SCHEME D OH E a -Ar H 2 2 02H n I THPi) 5 i O'IHP XVI XVII ,|.I\=/\/\ CO2H THPO' 2 )n GTHP XVIII \i-substitlited 602K pentanor PGE v I V I THIPO I OTHP XIX OH 1, b CO H v g-substituted m s P anor PGE THPO 2)nAI OTI-IP u-substituted pentanor I3, l l-dihydro PGE REACTION scams E XXI.

THPO

XXII

For the first step in the preparation of the w-substituted pentanor prostaglandins, the appropriatehemiacetal precursors (XVII and XXI wherein Ar is aor B-furyl, aor B-thienyl, aor B-naphthyl, 3,4-dimethoxyphenyl, 3,4-methylenedioxyphenyl, 3,4,5-trimethoxyphenyl, phenyl, or mono-substituted phenyl wherein said substituent is halo, trifluoromethyl, phenyl, lower alkyl, or lower alkoxy, and n is l or 2) is caused to react with the disodium salt .of' the known carboxybutyltriphenylphosphonium bromide XVI), in a molar ratio of from 1:2 to 1:5. The products of this reaction (XVIII and XXlI)'may be converted to the arsubstituted pentanor prostaglandins as outlined in Reaction Schemes D and E and described above for the N-substituted carboxamide analogs.

Treatment of the appropriate w-substituted pentanor PGE analog with a substituted carbodiimide, for example dicyclohexylcarbodiimide, and p-phenylphenol in a molar ratio of 121210 in a solvent such as methylene chloride or chloroform provides after column chromatographic purification the desired p-biphenyl esters of w-substituted pentanor PGE analogs.

The alcohols suitable for use in the composition of the present invention are numerous; they are all characterized as saturated, aliphatic, tertiary alcohols having from 4 to carbon atoms. Such alcohols include, among others. t-butanol; 2,3-dimethyl-2-butanol; 3- methyl-Z-butanol; 2,3-dimethyl-3-pentanol; and 3- ethyI-B-pentanol. Because of low cost and availability, t-butanol is preferred in the process of this invention.

In some cases, the compositions of the present inven- C H ?CH CH CH CH Cb \Q V H M Ar 6 5)6 2 2 2 2 i XVII Al-substituted pentanor I3,l l--dihydro PGE2 tion are desirably administeredby aerosol spray. For such application, a halogenated hydrocarbon propellant of up to 2 carbon atoms is employed. The propellant may be any of the conventional propellants used in aerosol' formulations, for example halogenated hydrocarbons of the fluorohydrocarbon or fluorohalohydrocarbon type such as trichloromonofiuoromethane. dichlordifluoromethane. dichlortetrafluoroethane. monochlorotrifluoromethane, monochlorodifluoromethane and mixtures of any of these together or with other propellants. Typical of suitable propellants are those disclosed I in, for example, US. Pat. No. 2,868,691 and sold under the trademark Freon.

The examples to follow are illustrative and in no way limit the scope of the appended claims.

EXAMPLES I-XIV By use of pharmaceutical compositions of this invention, the bronchodilator activity of the prostaglandin can be successfully retained for long periods of time at elevated temperatures. This is especially important for use in aerosol bronchodilator formulations.

The Table below demonstrates the effectiveness of t-butanol containing preparations of prostaglandin E in retaining potency for protecting guinea pigs against histamine-induced bronchospasms after storage at elevated temperatures. The stability of E-series prostaglandins used in increasing nasal patency. induction of labor, induction of abortion, and fertility control will be equally enhanced by the compositions of this invention.

Prostaglandin Weight Ratio v Example (wt in mg) PGE:tbutanol:Freon Conditions 2 Protection 1 1.6 mg PGE 1314500 2 weeks! 0C. 72 11 1.61 mg POE: 1:. 62 m 1.6 mg Pot-3 l: 70 l\' 1.6 mg PGE; 1160:8500 2 weeks/50C. 83 V 1.6 mg. PGE: 1:500:7600 79 \'1 1.6 mg PGE 1:950:6700 76 \'11 1.5 mg PGE: 1:160:8500 50 V111 1.5 mg PGE 1520:8500 71 1X mg POE- 'mitle 1260:8500 l2 \veeks50C. 75 X 1.5 mg PGE- -imide" 1520:8500 75 X1 3 mg PGE I: I2 \t-e'ckssmc. .79 X11 3 mg PGE: 1: 75 X111 3 mg PGE: 1: 79 XlV Control fresh PGE -imide 6-1 XV 1.5 mg PGE: 1: (I XVl 1.5 mg PGE -imide 131505600} 2 weeks/60C 0 Sealed in ampules. "'Stock solutions diluted to 56-100 mcgjml. with ethanol or water.

These diluted solutions were nehulized into a perspec box and the guinea pigs were exposed to the direct spra for one minute with an additional minute alloaetl for inhalation. The guinea pig was then placed into another box into which a histamine solution (2 mg./ml.l had been spray ed for one minute. A suhjecthe evaluation of the breathing pattern in the pig was made after 60 to 75 seconds in this atmosphere 10 no effect. 4 convulsions).

(S Control Evaluation 4 S Experimental Evaluation) ,1 Pmlecuo" F. Control Evaluation N-acetylprostaglandin E;- carhoxamitle These samples formulated with ethanol in place of t-hutanolv EXAMPLE XV PGE for Infusion mg. PGE, is placed in each of a series of vials; To

each vial is added one m1. t-butanol alcohol. The solutions may be diluted with 0.9% saline solution for infusion.

EXAMPLE XVl N-Benzoyl-Prostaglandin E- ,-Carboxamide for Aerosol i N-benzoy1-Prostaglandin E-gCLll'hOXfllTlh-C 10 mg. t-hutyl alcohol 2 g. Freon l l5/Freon 114 (40/60 w/w) to 10 g.

2. The composition of claim 1 wherein said prostaglandin is present in the amount of from about 0.010 to 0.100%by weight.

3. The composition of claim 1 wherein said prostag landin is PGE, or PGE 4. The composition of claim 1 wherein said prostaglandin is a PGE carboxamide of the formula:

wherein R is methyl or phenyl.

5. 'The composition of claim 4 wherein R is methyl. 6; The composition of claim 4 wherein R is phenyl. 7. The composition of claim 1 wherein said alcohol is t-butyl alcohol.

8. The composition of claim 1 also containing from about 1 to 10 parts by volume, based on said alcohol, of a halogenated hydrocarbon propellant of up to 2 carbon atoms. 

1. A STABILIZED PHARMACEUTICAL COMPOSITION COMPRISING A BIOLOGICALLY ACTIVE PROSTAGLANDIN OF THE E-SERIES AND A SATURATED ALIPHATIC TERTIARY ALCOHOL HAVING FROM 4 TO 10 CARBON AROMS, SAID PROSTAGLANDIN BEING PRESENT IN THE AMOUNT OF FROM ABOUT 0.005 TO 0.500% BY WEIGHT.
 2. The composition of claim 1 wherein said prostaglandin is present in the amount of from about 0.010 to 0.100% by weight.
 3. The composition of claim 1 wherein said prostaglandin is PGE1 or PGE2.
 4. THE COMPOSITION OF CLAIM 1 WHEREIN SAID PROSTAGLANDIN IS A PGE2 CARBOXAMIDE OF THE FORMULA:
 5. The composition of claim 4 wherein R is methyl.
 6. The composition of claim 4 wherein R is phenyl.
 7. The composition of claim 1 wherein said alcohol is t-butyl alcohol.
 8. THE COMPOSITION OF CLAIM 1 AND ALSO CONTANING FROM ABOUT 1 TO 10 PARTS BY VOLUME, BASED ON SAID ALCOHOL, OF A HALOGENATED HYDROCARBON PROPELLANT OF UP TO 2 CARBON ATOMS. 